1. Field
Example embodiments may provide a CMOS image sensor, for example, a CMOS image sensor having a honeycomb structure in which photodiodes may have a hexagonal shape and two unit pixels may share a floating diffusion (FD).
2. Description of the Related Art
In a related art charge coupled device (CCD) or CMOS image sensor (CIS), a photodiode (PD) may convert incident light into an electric signal based on the light's wavelength. It is desirable to collect incident light with a quantum efficiency of 1 with respect to all wavelength bands, that is, all of incident light is collected.
A unit pixel in a related art CIS may include a single PD and four transistors. The four transistors may include a transfer transistor that may transfer photo-generated charge collected at the PD to an FD, a reset transistor which may reset the FD by setting an electric potential of a node to a desired value and discharging the charge, a drive transistor which may function as a source follower buffer amplifier, and/or a selection transistor which may enable addressing through switching.
As size of related-art CIS's decrease, the size of an active pixel sensor receiving light may also decrease. A PD, which is influences characteristics of the CIS, may need to remain at a set size even if the size of an active pixel sensor is decreased. Sharing a circuit may overcome this problem.
If unit pixels in a pixel array have a square shape and a degree of integration increases to achieve higher resolution, the length of a pixel array may increase, potentially resulting in increased parasitic resistance and/or parasitic capacitance. A pixel pitch between unit pixels may also increase. An image sensor having a honeycomb structure may prevent or reduce these problems. A pixel architecture in which unit pixels share a circuit in the honeycomb structure may be desired.